Cosmo Kramer

Now that I have my car boosted, when the kickdown relay is activated at full throttle, the car hits the limiter before it shifts up, before it was supercharged it was fine. I have the bowden cable adjusted properly, maybe even on the loose side. On my next drive I am going to pull out the kickdown relay and see what happens, I can always shift it manually if need be, plus I don't really need to rev it that high now.

Has anyone else ever experienced this?

Tampa 928s

??? what do you mean shifts high, you mean every shift goes to red line?
Your Wot has nothing to do with the shift points. Check your adjustment again, check your vacuum line and connections on the tyranny.

Cosmo Kramer

On the cars with auto trannys there is an electrical switch under the gas pedal that holds the gear longer/forces a downshift.

Tampa 928s

Thought you were talking about the WOT switch, I did a switch bypass on mine and use it when I want. Just check it with a meter should be open until you press it.

Brett928S2

Hi

I had exactly the same problem with my Nitrous...i.e. when I hit the Nitrous button the revs would rise so fast that it sort of hit the rev limiter BEFORE the autobox shifted up as it should do....

I came to the conclusion that the shift on the box could not cope with such a drastic increase in revs in so short a period of time.... so I was sort of "beating" the autobox shift...

I could never cure it, although like you I discovered that manually shifting the autobox worked pretty much...

My eventual answer was to get John Speake to blow me a chip with the rev limiter removed, although he didn't actually remove it, he set it as high as he could at 9700 revs...

What I then discovered was that the box would shift up at around 6500 to 6700 instead of the usual 6375 it was designed to do....and no limiter to come in....

Have a word with John and he would happily do the same with a chip for you I would think...

All the best Brett

Cosmo Kramer

Thanks Brett, that is exactly what it is doing. I am going to try and see what it is like with the relay out. I wish there is a way that I could lower the shift point in the transmission when the kickdown circuit is active.

IcemanG17

have you tried reducing tension in the bowden cable? That is the primary control of shift points.....the firmness of the shifts is determined by the amount of vacuum at the modulator....

For example our lemons racer would shift WAY too high for an 84 US...6200 to 6500rpm when red is indicated at 6000......it was a serious problem during our 1st race....so we disconnected the bowden cable completely...WOW what a difference.........now the tranny wants to instantly shift to a higher gear all the time...so you use the shifter to hold the gear you want...as soon as you change gears (typically 2-3 or 3-2 for us) it does it regardless of if you are at WOT or cruise...

Cosmo Kramer

I have put a bit of slack in it but still persists, shifts are fine until the kickdown switch is activated at WOT, then it won't shift shift up. I don't want to try and manage lifting on the pedal at the precise moment it shifts. Basically the faster it revs the higher the rpm's are when it shifts. When I had some belt slip and is was down to 3 psi around 6000 rpm it would shift, not that it is at 8 psi it hits the limiter on the 1-2 and 2-3 shift in drive at wot.

porsche928guy

Ted...did you cure the hard shifting?

John Speake

It might be possible to modify the kick down relay. There is probably some filtering in there which is slowing its response.

Brett928S2

Hi

I know exactly what you mean and like you I tried EVERYTHING with the cable etc to try and LOWER the shift point...I "thought" if I could lower it to say 5000 then even with the "over-shifting" it would hopefully change up at around 6000 which would be BEFORE my 6375 limiter...

It didn't work..... which is why I went to John

To me it "seems" that the box is just not capable of shifting that fast when the revs are rising that fast....

To anyone reading this without a blown or turboed or Nitrous motor ,I realise it sounds like we are talking rubbish but it DOES actually happen precisely like Cosmo and I are saying...

My way round it was the only option that I could think of and at least it DOES work in that the box eventually shifts and you get the advantage of no limiter leaning out the engine which is a VERY good thing on a Nitrous ENGINE LOL

All the best Brett

anonymousagain

Ted, even if you disable the kickdown switch and manually shift it, you will likely need to lower your "target" shift point dramatically. By the time you cycle through eyes-to brain-to hand/shift-to tranny-to next gear, you'll have gone through hundreds of rpm's...and if you're sleeping or distracted for a second, you'll miss the window.

Brett's suggestion for a higher limiter makes sense, although personally I'd look for just a bit higher to allow for the shift yet still provide backup if you forget you left it in 2nd

First order is to make sure the SC will take a slight overrev to 6500 or 6700...I'd expect it'd be fine, since you are not at high boost, but better to check and account for it (tune with that expectation?) then get surprised later that something isn't ready for an occasional spike.

Good luck!

Cosmo Kramer

Well took it out with the relay out and no difference. Manually shifted from 2-3 and still would not shift and hit the limiter. Put the relay back in and kept loosening the bowden cable. I slacked it off until the car would shift, the socket extends past the ball about 1/4". Only thing now it won't kick down into 2 at say 40 - 50 mph but that is OK I can do it myself with the shifter.

Cosmo Kramer

Yes I put a one way valve on the vacuum line and it is all good now.

IcemanG17

This is the problem we were having......the drivers would lift briefly at say 6000+ trying to get it to shift....but heres the problem...on the L jet, by doing that you come off the WOT loop and go back (briefly) to the 02 loop which will try to go stoic which is NOT a good idea at 6000+rpm...I'm sure it helped kill that engine...

Try this...disconnect the kickdown and bowden cable.... Start with the trans in 2 and shift yourself...... My guess is it will shift somewhat short from 1-2 and then it will shift when you tell it from there....

Its easy to try...